The present device relates to medical devices, and specifically to improvements to devices such as sphincterotomes, also known as papillotomes.
In endoscopic, or other minimally invasive surgery, generically referred to herein as endoscopic surgery, a sphincterotome may be used in conjunction with an endoscope to provide surgical cutting inside a patient. Specifically, a sphincterotome is used during certain procedures to make an incision in a sphincter. For example, a common treatment of cholecystitis includes the removal of gallstones from the common bile duct. This is frequently done endoscopically with the use of a duodenoscope. The common bile duct proceeds from the junction of the common hepatic duct with the cystic duct, which is open to the gall bladder, and merges with the pancreatic duct, forming the ampulla of Vater, which itself opens into the duodenum at the papilla of Vater. The sphincter of Oddi is a muscular ring that controls passage of fluid from the ampulla of Vater into the duodenum. For removal of gallstones in an endoscopic procedure, access to the common bile duct for removal of gallstones is eased using a sphincterotome to incise or sever the sphincter of Oddi. The sphincterotome is introduced through the duodenoscope and guided through the duodenum to the common bile duct. Once the sphincterotome is guided into the sphincter, its cutting element, commonly a needle knife or cutting wire, is used to incise the sphincter, and thereby improve access to the bile duct and impacted gallstones.
Another example of a common procedure utilizing a sphincterotome is endoscopic retrograde cholangiopancreatography (ERCP), a diagnostic visualization technique used for variety of clinical applications. In this procedure, a contrast fluid such as a radio-opaque dye is introduced through a tube into the ampulla of Vater. A sphincterotome is often employed to provide access through the sphincter of Oddi in the same manner as described above. ERCP is often used in diagnosis of cholecystitis, as well as in the diagnosis and treatment of other conditions of the pancreatic and common bile ducts and related structures.
As illustrated in FIG. 1, a typical sphincterotome 100 includes a polymer tubular shaft 102 made of PTFE (polytetrafluoroethylene) or another flexible material. An electroconductive filament 104, also called a drive wire, is disposed in a lumen 106 running through the shaft 102. The distal end of the filament 104 is connected or anchored to the distal end of the shaft 102. A short segment of the electroconductive filament 104 near the distal end thereof is disposed outside of the shaft 102 for use as an electrocautery cutting wire 108. The proximal end of filament 104 is connected to the proximal handle assembly 110 such that actuation of the handle assembly 110 partially retracts (i.e., pulls in a proximal direction) the filament 104 relative to the polymer shaft 102. This actuation results in the distal end of shaft 102 bowing to form an arc 112, with the exposed filament forming a secant of the arc 112 so as to form a cutting wire 108. Electric current passed through the filament 104 from an electrode 114 in the handle assembly 110 enables the cutting wire 108 to act as an electrosurgical cutting element that may be used effectively to cut and cauterize tissue, such as the sphincter of Oddi in the example procedures described above.
One problem that may occur during use of a sphincterotome is that tissue adjacent the sphincter of Oddi may inadvertently be cut. Specifically, the papillary tissue around the sphincter often protrudes as a folded surface. During a sphincterotomy, it is most preferable to incise only the desired tissue of the sphincter to permit cannulation thereof. However, the adjacent papillary folds may inadvertently be cut or otherwise damaged by a portion of the cutting wire 108 adjacent the portion thereof that is actually incising the sphincter. Another problem that can occur is that current may arc from the exposed cutting wire to the endoscope or another structure. If this occurs, the cutting wire may break, rendering the sphincterotome useless, and potentially even releasing one or more wire fragments, which may pose an injury risk. For these reasons, it is desirable to have only a small cutting wire portion exposed such that it can be used in a targeted fashion for a sphincterotomy. Physical structural constraints of the sphincterotome prevent this from being accomplished by having only a small enough arc 112 to target the cutting wire in this manner. As a result, some sphincterotomes have included a coated portion of the cutting wire. These devices typically use PTFE or another polymer in the form of a sleeve. These coating sleeves also suffer from shortcomings. For example, during ordinary assembly and use, the sleeve may be nicked or split (e.g., by contact with an elevator of an endoscope), or may migrate longitudinally in a manner that exposes the wire and negates the intended insulating effect. This type of sleeve coating also increases the outer diameter of the cutting wire. Therefore, there is a need for a sphincterotome wire coating that provides desirable electro-insulation, resists damage, and does not significantly increase cutting wire diameter.